1. Technical Field
The present invention relates to an entire solid lithium secondary battery.
2. Description of the Related Art
An entire solid lithium secondary battery is a lithium secondary battery including an electrolyte layer formed of a solid electrolyte. The entire solid lithium secondary battery has higher safety and higher energy capacity than a lithium secondary battery including a liquid electrolyte containing a flammable solvent. The entire solid lithium secondary battery comprises a cathode, an anode, and a solid electrolyte layer. The solid electrolyte layer is disposed between the cathode and the anode. A cathode active material layer included in the cathode is in contact with the solid electrolyte layer. The cathode active material layer contains a cathode active material capable of storing and releasing lithium ions. Similarly, an anode active material layer included in the anode is in contact with the solid electrolyte layer. The anode active material layer also contains an anode active material capable of storing and releasing lithium ions. The lithium ions travel through the solid electrolyte layer. In other words, in the entire solid lithium secondary battery, the lithium ions migrate between the cathode active material layer and the anode active material layer in association with the redox reaction on the cathode and anode. Due to this migration, the entire solid lithium secondary battery is charged and discharged.
Even when the solid electrolyte formed of an oxide is exposed to the air, the high stability and the high safety thereof are maintained. A. M. Glass et al., “Ionic conductivity of quenched alkali niobate and tantalite glasses”, Journal of Applied Physics, 49(9), 1978, pp. 4808-4811 discloses that amorphous LiNbO3 and amorphous LiTaO3 have lithium ion conductivity substantially equal to each other. Japanese Patent Application laid-open Publication No. 2010-251257A discloses a crystalline solid electrolyte material formed of a complex containing LiNbO3 and LiNb3O8 at a specific mixture ratio. Japanese Patent Application laid-open Publication No. 2010-251257A further discloses that amorphous LiNbO3 has higher lithium ion conductivity than crystalline LiNiO3.